Cells transformed by temperature-sensitive (ts) mutants of murine sarcoma virus (MSV) offer a unique and well controlled mammalian cell system for the analysis of MSV gene functions required for transformation of cells and should aid in the identification of viral gene products involved in malignant transformation. The objectives of this proposal are: 1) to isolate and characterize additional ts mutants of MSV, 2) to use ts mutants of MSV in temperature shift experiments, with and without metabolic inhibitors, to elucidate how MSV genes elicit transformation, and 3) to undertake a detailed study designed to reveal primary virus-induced changes following temperature shifts using NRK cells transformed by the cold-sensitive mutant of MSV. Central to this approach will be the experiments designed to identify by high resolution two-dimensional polyacrylamide gel electrophoresis newly synthesized proteins and glycoproteins in cell extracts and surface membrane fractions of cold-sensitive MSV-transformed cells following temperature shifts.